This invention relates generally to filter devices and, more particularly, to fuel system filters for small particulate contaminants.
It is well-known that the mechanical cleaning of a filter surface can be accomplished by having a brush or scraper drag along the filter surface where deposits have accumulated. In certain configurations, the brush or scraper is mounted at one end between two walls but with a significant portion of the brush or scraper projecting beyond the walls. Such configurations are shown in U.S. Pat. No. 148,557 (Gillespie et al.); U.S. Pat. No. 556,725 (Farwell); U.S. Pat. No. 740,574 (Kohlmeyer) and U.S. Pat. No. 793,720 (Godbe). In conventional filter systems, the particulate contaminants are driven off the filter surface and are deposited in a hopper or tank along with the fluid being filtered, thus discarding large amounts of the fluid being filtered.
The use of a brush, or high speed cleaning spray, disposed between a pair of walls for cleaning a cylindrical filter is known in the art, as is disclosed in U.S. Pat. No. 5,423,977 (Aoki et al.) and U.S. Pat. No. 5,595,655 (Steiner et al.) and Swiss Patent No. 22,863 (Zingg). Another variation employs a backwash that drives the particulate contaminants off of the cylindrical filter, as is disclosed in U.S. Pat. No. 3,338,416 (Barry).
One desirable use for fuel oil filter systems of the present invention is in ships. Prior art ship fuel oil systems use conventional filter cartridges for cleaning the fuel in-line. However, these filter cartridges require frequent replacement which, in turn, requires the fuel flow to be interrupted during replacement. Interruption of the fuel oil flow will shut down the ship's main engines, thereby rendering the ship incapable of maneuvering. This can be catastrophic where the ship is in tight quarters, e.g., during docking or navigating through narrow passageways, or during storms, or during battle with regard to warships.
Furthermore, there are additional costs of having to store sufficient replacement cartridges onboard, the logistics involved in shipping and disposing the cartridges to and from the ship, and the labor costs involved in replacing the cartridges.
In addition, shipboard fuel oil straining is a specialized straining process. In particular, the fuel oil flow is initially pre-strained for gross particulate contaminants, such that any particulate contaminants remaining in the fuel oil flow are extremely small (e.g., &lt;100 microns, with a large percentage being less than 25 microns). As a result, where these small particulate contaminants are captured by a downstream strainer (e.g., a wedge wire screen strainer), both on and within the strainer surface, and then later dislodged during the strainer cleaning process, these extremely small particulate contaminants do not fall by gravity toward a drain but remain suspended in the fuel oil and will re-attach to the strainer surface. Therefore, there remains a need for a cleaning device that can dislodge such extremely small particulate contaminants off of the downstream strainer surface, as well as from within the strainer surface, and then ensure that these particulate contaminants flow out through the drain rather than re-attaching to the strainer surface.
Thus, there is a need for an improved system for removing undesired particulate contaminants from a fuel oil flow and without interrupting that fuel oil flow to the engines, while minimizing the amount of fluid removed therewith. It is to just such a system that the present invention is directed.